a. Field of the Invention
This invention relates to voltage regulators and related control systems.
b. Related Art
A step type voltage regulator is a device which is used to maintain a relatively constant voltage level in a power distribution system. Without such a regulator, the voltage level of the power distribution system could fluctuate significantly and cause damage to electrically powered equipment.
A step-type voltage regulator can be thought of as having two parts: a transformer assembly and a controller. A conventional step-type voltage regulator transformer assembly 102 and its associated controller 106 are shown in FIG. 1. The voltage regulator transformer assembly can be, for example, a Siemens JFR series. The windings and other internal components that form the transformer assembly 102 are mounted in an oil filled tank 108. A tap changing mechanism (not shown) is commonly sealed in a separate chamber in the tank 108.
The various electrical signals generated by the transformer are brought out to a terminal block 110 and external bushings S, SL, L for access. The terminal block is preferably covered with a waterproof housing. An indicator 112 is provided so that the position of the tap as well as its minimum and maximum positions can be readily determined.
A cabinet 114 is secured to the tank to mount and protect the voltage regulator controller 106. The cabinet 114 includes a door (not shown) and is sealed in a manner sufficient to protect the voltage regulator controller 106 from the elements. Signals carried between the transformer or tap changing mechanism and the voltage regulator controller 106 are carried via an external conduit 116.
The tap changing mechanism is controlled by the voltage regulator controller 106 based on the controller's program code and programmed configuration parameters. In operation, high voltage signals generated by the transformer assembly 102 are scaled down for reading by the controller 106. These signals are used by the controller 106 to make tap change control decisions in accordance with the configuration parameters and to provide indications of various conditions to an operator.
The regulator control configuration parameters are commonly referred to as "setpoints". These setpoints typically include forward and reverse settings for voltage level thresholds, bandwidth and time delay. The setpoints can also include settings for upper and lower voltage limit control.